Got a 99 GT convertible that picks up a miss between 1400 and 2500 RPM. I changed the plugs and all COPs no codes. Iam not sure if its a miss or something out of balance the car will start to shake. Does it in park being just revved up. I have checked the grounding pulse to the COPs and it checks good. Any ideas??

Would low fuel pressure cause a misfire around 1800 when revved up. Checked pressure today and at idle it runs 21 PSI when motor speeds up goes to about 36 PSI. Normal or to low. Also if is was a low fuel misfire should it throw a code ??

Ok took to shop today they found no misfire and fuel pressure ok. To him seems to think its something out of balance . Putting on the lift to check mounts and flywheel. We checked balancer nothing there. Feel it in park when revved up....